Pebble heater and method of converting hydrocarbons



June 29, 1954 H. A. DUTCHER 2,682,497

PEBBLE HEATER AND METHOD OF CONVERTING HYDROCARBONS Filed April 10, 19502 Sheats-Sheet l INVENTOR. H. A. DUTCHER ATTORNEYS June 29, 1954 H. A.DUTCHER PEBBLE HEATER AND METHOD OF CONVERTING HYDROCARBONS Filed April10, 1950 2 Sheets-Sheet 2 H.A. DUTCHER A 7' TORNEKS Patented June 29,1954 PEBBLE HEATER AND METHOD OF CONVERTING HYDROCARBONS Harris A.Dutcher, Bartlesville, 0kla., assignor to Phillips Petroleum Company, acorporation of Delaware Application April 10, 1950, Serial No. 155,037

13 Claims. 1

This invention. relates to pebble heat exchangers. In one of its morespecific aspects, it relates to the conversion of heavy petroleum oil orresiduum. In another of its more specific aspects, it relates to a meansfor introducing heavy petroleum oil into a reaction chamber. In anotherof its more specific aspects, it relates to improved pebble heatexchange apparatus.

Thermal conversion processes which are carried out in so-called pebbleheater apparatus utilize a. fluent mass of solid heat exchange material,which mass is ordinarily heated to a high temperature by passing hot gastherethrough in a first direct heat exchange step and is then caused tocontact fluid reactant materials, furnishing heat thereto. in a seconddirect heat exchange. In the conversion of heavy petroleum oils inpebble heater apparatus, it is known to introduce a stream of theheavypetroleum oil or residuum as reactant material directly into theupper. portion of a reaction chamber which contains a fluent mass of.pebbles heated asabove described; In such operation, it has been foundthat a very poor distribution of the heavy petroleum fraction isobtained throughout the re- 1.;

action chamber and the hot fluentpebble mass contained therein. Anotherproblem which has been encountered in such an. operation is thatexcessive coking occurs by reason of the direct contact between theheavy petroleum fraction and the heated pebbles. For the above reasonsnon-uniform conversion of the heavy petroleum oil isobtained and anexcessive amount of such oil is converted to coke rather than to thedesired lighter hydrocarbon materials.

Broadly speaking, this invention comprises a meansand method forconverting heavy petroleum oils to lower boiling hydrocarbon materials,suchas ethylene, propylene, and highly aromatic gasoline-type materials.The means by which this" improved operation. is obtained is an improvedpebble heater apparatus which utilizes the conventional Z-chamber devicebut which has, in addition, at. least one other pebble chamber which isutilized for coating pebbles which are at a relatively low temperaturewith the heavy petroleum oil utilized as the heavy reactant materialcharge stock for the system. The method of converting the heavypetroleum oil fraction to the lower boiling hydrocarbon materials hasthe improvement of better distribution of the oil throughout thereaction chamber and a lesser direct contact between the oil chargestock and the hot pebbles from the pebble heater chamber;

Conventional pebble heater chambers of peb- 2. ble: heater apparatus aregenerally formed as cylinders in which a solid heat exchange material iscollected. in the form of a moving bed. Hot heat exchange gasesarepassed upwardly through the cylindrical bed, sometimes being introducedthereinto at the periphery of the bed and at its. lower end, andsometimes through a refractory arch which supports themoving pebble bed.At other times, heat is supplied to the heating chamber by supplying afuel to the lower portion of the pebble bed within the. heater chamberand burning. the fuel on. the surface of the pebbles so as to heat thepebbles by combustion and further. heat the pebbles by passing theresulting combustion gas upwardlythrough the downflowing fluent mass ofpebbles and in direct heat exchange therewith- The heated pebbles areintroduced into the upper portion of. a reaction chamber and thereactant materials when comprising. heavy petroleum: oil or. residuumhave been conventionally introducedv asaIfluidstreami directly onto thesurfaceof the hot pebbles from the pebble heater chamber and flowdownwardly. through the reaction chamber concurrent the flow of the hotsolid heat exchange material, thereby obtaining theheat necessary forthermalconversion of the heavy petroleum or. residuum fraction.

Solid heat exchange material which is conventionally used in pebbleheater apparatus'is generally called pebbles. The term pebbles asus'edherei'n denotes any'solid refractory material of flowable size andform, having strength which is suitable to'carry large amounts of heatfrom the pebble heatingchamber to the reaction chamber without rapiddeterioration or substantial breaking. Pebbles which are satisfactorilyused in pebble heater apparatus are ordinarily substantially sphericalin shape and range from about g inch to about 1 inch in diameter. Inhigh temperature processes, pebbles having a diameterof between aboutinch. and /2 inch are'preferred; The pebbles must be formed ofarefractory material which willwit-hstand temperatures at least as highas the highest temperature attained inthe pebble heater chamber. Thepebbles must also be capable of withstanding, temperature changes withinthe apparatus. Refractory materials, such as metal alloys, ceramics, or.other satisfactory material may be utilized to form such pebbles.Silicon carbide, alumina, periclase, thoria, beryllia, Stellite,zirconia, and mullite may be satisfactorily used to form such heattransfer'pebbles or may be used in admixture'wit'lieach. other'or withother ma.-

terials. Pebbles formed of such materials when properly fired serve verywell in high temperatures. Some pebbles, such as mullite-alumina pebbleswithstand temperatures as high as 3200" F. and above.

An object of this invention is to provide an improved pebble heaterapparatus. Another object of the invention is to provide improved meansfor introducing a heavy petroleum fraction charge stock into a reactionchamber of pebble heater apparatus. Another object of the invention isto provide a method for introducing a heavy petroleum fraction chargestock into a reaction chamber of pebble heater apparatus. Another objectof the invention is to provide improved means for reducing cokeformation in the thermal conversion of a heavy petroleum fraction chargestock. Another object of the invention is to provide an improved methodfor reducing coke formation in the thermal conversion of a heavypetroleum oil charge stock. Other and further objects and advantageswill be apparent to those skilled in the art upon study of theaccompanying discussion andthe drawings.

Understanding of th invention will be facilitated upon reference to thedrawings in which Figure 1 is a diagrammatic elevation of the pebbleheater apparatus of this invention. Fig-- ure 2 is a modification of thepebble throat arrangement between the pebble heater chamber and reactionchamber of the device shown as Figure 1 of the drawings. Figure 3 is ahorizontal cross-section taken along the line 3-3 of Figure 2. Figure 4is a schematic showing of a preferred modification of the pebble heaterapparatus of this invention. Figure 5 is another diagrammatic elevationof a modification of the pebble heater device of this invention.

Referring specifically to Figure l of the drawings, pebble heaterchamber II comprises outer shell I2, which is closed at its upper andlower ends by closure members I3 and I 4, respectively. Pebble inletconduit I5 and gaseou effluent outlet conduit IB are provided in closuremember I3 and pebble outlet conduit I'I extends downat least a portionof closure member I4, communicating through that closure member with theinterior of pebble heater chamber I I. Pebble outlet conduit IT in thelower end portion of chamber II has an enlarged cross-section in itslower end portion, which enlarged conduit portion is connected toclosure member I9 in the upper end of shell 2| which forms reactionchamber 22. Gaseous eifluent outlet conduit 23 is provided in closuremember I 9. The lower end portion of shell 2I is closed by closuremember 24 and fluid conduit 25 is connected to closure member 24,communicating through that closure member with the interior of pebblechamber 22. Conduit 25 preferably extends as a bustle ring at least aportion of the way around closure member 24. Pebble outlet conduit 26 isprovided in closure member 24, which pebble outlet conduit is connectedat its lower end with the lower end portion of elevator 21. Pebble flowcontroller 28, which may be a conventional star valve, a table feeder, agate valve, or the like, is provided intermediate the ends of pebbleoutlet conduit 26. Elevator 2'! is connected at its upper end portionwith pebble inlet conduit I 5 which is connected at its lower end withclosure member I3 of pebble heater chamber I I. Elevator 21 may be of abucket type, a helical conveyor, 2. gaslife type elevator, or the like.

Contact chamber 29, which comprises shell 3I closed at its upper andlower ends by closure members 32 and 33, respectively, is connected toconduit I5 intermediate its ends by conduit member 34 which is connectedto chamber 29 at clo sure member 32. Pebble outlet conduit .36 extendsbetween closure member 33 of shell 3| and the enlarged portion ofconduit II between the bottom of chamber I I and the upper end portionof chamber 22, Pebble flow controller 35 is provided intermediate theends of pebble conduit 36. A perforate member 3'! is provided in thelower portion of a section of outlet conduit 36 and collector chamber 38is affixed to the lower portion of conduit 35 and around perforatemember 31 therein. Fluid outlet conduit 39, which is provided with flowcontrol valve 4i, extends between the lower end portion of collectorchamber 38 and charge stock storage chamber 42. Charge stock supplyconduit 43 extends into storage chamber 42 and charge stock outletconduit M, which is provided therein with flow control valve 45, extendsbetween the lower portion of storage chamber 42 and pump 46. Chargestock supply conduit 41 extends between pump 45 and the lower endportion of pebble conduit 34 which is connected at its lower end withcontact chamber 29. Flow control valve i8 is provided intermediate theends of charge stock supply conduit 41.

In the operation of the device disclosed above, pebbles are supplied tothe upper end portion of pebble heater chamber II and form a fluentcontiguous mass with that chamber, which fluent pebble mass gravitatesdownwardly through that chamber. A fluid heating material is introducedinto the lower portion of chamber II. The fluid heating material may bea hot combustion gas which is introduced into the lower p on of chamberII through inlet conduit Ill. The combustion gas flows upwardly throughthat chamber countercurrent the flow of solid heat exchange materialtherein. The heating material may also by a combustible fuel, togetherwith air, which fuel is burned in the presence of the fluent pebbles,imparting heat to those pebbles as a result of the combustion. Resultingcombustion gases are allowed to flow upwardly through chamber I Icountercurrent the flow of pebbles therein. The hot combustion gas heatsthe pebbles in a direct heat exchange relation and after imparting alarge portion of its heat to such pebbles, the gaseous efiiuent materialis removed from chamber I I through effluent outlet conduit I6. Thepebbles are heated to a temperature within the range of 2000" F. to 3200F., preferably within the range of 2500 F. to 3000" F., in chamber IIand are gravitated from that chamber through conduit I'l into reactionchamber 22 in which they form a fluent contiguous pebble bed.

A second portion of pebbles is introduced into chamber 29 throughconduit 35 and forms a fluent contiguous mass within that chamber. Heavypetroleum oil or residuum is pumped by means of pump 45 through conduit41 and is sprayed onto the surface of the pebbles which are introducedinto chamber 29. The heavy petroleum oil generally has an API gravitywithin the range of 10 to 25, preferably between 15 and 20. The pebbleswithin chamber 29 are at a temperature within the range of from 300 F.to 800 F. It is preferred that the temperature of those pebbles bemaintained within the range of from 350 F.

to 700 F. As the pebbles are introduced into,

chamber 29, the heavy petroleum fraction is sprayed onto the surface ofthose pebbles and asthe mass of pebbles moves downwardly through chamber29 the coating of oil is evenly distributed over the surface of theindividual pebbles. The oil coated pebbles are gravitated from the lowerportion of chamber 29 through conduit 36. As the oil coated pebbles flowthrough conduit 36, any excess heavy oil or residuum which is notintimately coating the pebbles is separated from the pebbles and passesinto an excess oil separation means comprising perforate member 31' andcollector chamber 38. The oil is removed from chamber 38 through conduit39 into storage chamber 42. The oil is then recycled to: the upperportion of chamber 29 through conduit 42, pump 46, and conduit 41.

The oil coated pebbles are introduced into the enlarged portion ofconduit H and flow downwardly in admixture with the heated pebbles frompebble heater chamber ll. pebbles and the oil coated pebbles are evenlydistributed as they gravitate together into reaction chamber 22. Theheated pebbles from pebble heater chamber I I provide the heat necessaryfor the conversion of the coatin of heavy oil on the pebbles fromchamber 29. The heavy oil is raised to reaction temperature at aslightly slower rate than is obtained in the introduction of such oi1directly onto the hot surface of the highly heated pebbles. For thatreason, a considerably greater portion of the heavy residuum orpetroleum oil is converted to hydrocarbon materials of lower boilingpoint than the residuum than was possible in the conventional method ofdirect introduction of heavy petroleum onto the highly heated pebbles. Asmaller proportion of coke is formed in this manner than by the methodof direct introduction of residuum onto highly heated pebbles. Resultingreaction products which are in a gaseous or vaporous state are removedfrom chamber 22.

Removal of the reaction products may be made through gaseous efliuentoutlet conduit 23 in closure member I 9 or may be through fluid conduit25. In the preferred method of operation, the gaseous effluent isremoved through conduit 23 and a gaseous material, generally one whichis inert to the reaction being carried on within chamber 22, isintroduced into the lower portion of that chamber through conduit 25.Steam or a normally gaseous hydrocarbon, such as propane or butane, issatisfactorily utilized as the -inert material introduced throughconduit 25. The introduction of such gaseous material into the lowerportion of the pebble bed within chamber 22 materially reduces thetemperature of the pebble mass by extracting heat therefrom, which heatis carried into the upper portion of the pebble bed within chamber 22 bythe inert gaseous material and the inert gaseous material issubsequently removed from chamber 22 through gaseous eiliuent outletconduit 23. The pebbles which have been cooled by the reaction and heatexchange within chamber 22- are removed from that chamber throughconduit 26 and the flow thereof is controlled through conduit 26 bymeans of pebble flow control device 28 which may be, as pointed outabove, a conventional star valve, a table feeder, a gate valve, or otherconventional flow control device. The pebbles, which have been cooledfor better handling, are elevated by elevator 21 and are introduced intothe upper The heated end portion of conduit l5, A portion of these thelower portion of that chamber.

cool pebbles is removed from conduit 15 through conduit 34. The flow ofpebbles through chamber 29 is controlled by means of pebble flowcontroller 35 in conduit 36. The remaining portion of the pebbles isintroduced into the upper por tion of chamber H through conduit I5 andthe pebbles are raised to a high temperature therein as described above.

Referring particularly to Figure 2 of the drawings, conduit I! ismodified by providing it with a baffle member 5! which is supportedtherein by support members 52. Baffie. member 51- is smaller in diameterthan the inner diameter of conduit H by more than at least two pebblediameters. Conduit 36 extends through the wall of conduit I? andterminates at a point directly above bafile member 51. The dispositionof baffle member 5| with respect to conduit I! is shown in Figure 3 ofthe'drawings. ,Bafiie member 5| is preferably disposed so as to form anannulus between its periphery and conduit ll. Excellent admixing betweenhot pebbles which pass downwardly through conduit I! and oil coatedpebbles which gravitate into conduit I! through conduit 36is aided bybaille member 5 i Referring particularly to the device set forth asFigure 4 of the drawings, parts which are the same as those disclosed inconnection with Figure 1 of the drawings, are indicated by likenumerals. Chamber 22 of Figure 4 is provided intermediate its ends witheiiiuent outlet conduit 53 which has flow control valve 54 providedtherein. Conduit 53 is preferably provided in the lower portion ofchamber 22 so that it can be adapted for the withdrawal of gaseouseffiuent from that chamber under conditions such that concurrent flow ofsolid heat exchange material and reaction products is obtained. Flowcontrol valve 55 is provided in effluent outlet conduit 23 in closuremember it of chamber 22. By such construction, it is possible to removethe gaseous reaction product from either the upper end portion ofreaction chamber 22 Or from a point in Auxiliary reactant material inletconduit 56 is shown by dotted. lines in the upper end portion ofreaction chamber 22 and surrounds a space adjacent the outlet end ofconduit ll. Inlet conduit 56, which is preferably in the form of aperforate header, is-

connected to reactant material supply conduit 43 36 is aided by bafliemember 5 I.

Contact chamber 58 differs from contact chamber 29 of Figure 1 in theincorporation of the collector chamber portion 59 at the lower end ofchamber 58, which collector chamber portion correspond to chamber 38shown in Figure 1 of the drawings. Collector chamber portion 59 isseparated from the upper portion of chamber 58 by means of a perforatepebble support member 6| which slopes downwardly across chamber 58 tothe inlet end of pebble outlet conduit 35.

Operation of the device shown as Figure l of the drawings is similar tothat set forth in the discussion of Figure 1 and differs particularly inthe introduction of additional reactant; material directly onto thesurface of the pebbles which are.

introduced into the upper portion of chamber 22. Although it is realizedthat such operation results in a considerably higher carbon formation,it is at times desirable to feed a greater quantity of resurface of therelatively cool pebbles from chamber 58 is obtained by varying the speedat which pebble flow controller 35 is operated. The ratio of oil coatedpebbles from chamber 58, or chamber 29 of Figure 1, to the heatedpebbles from chamber II is preferably maintained within a ratio ofbetween 1:1 to 1:3. The ratio of hot to oil coated pebbles and thequantity of oil introduced through inlet conduit 56 is such that theheavy oil is raised to a reaction temperature within the range of from1400 F. to 1600 F.

Although greater carbon formation is encoun tered by introducing thereactant material direct ly onto the surface of the pebbles in the upperportion of chamber 22 than is encountered when all of the oil isdistributed as a coating on cool pebbles, a lesser amount of carbonformation is encountered than in an operation in which all of the heavypetroleum fraction is introduced directly onto the surface of pebbleswhich have been heated to a high temperature. This mixed type ofoperation, however, lends flexibility to the over-all process of thisinvention.

Gaseous material which may be inert to the reaction carried on withinchamber 22 is introduced into the lower portion of that chamber throughconduit 25 and when the gaseous reactant materials are withdrawn fromchamber 22 through conduit 53 the inert gaseous material is alsowithdrawn through that conduit. When reaction products are withdrawnthrough eflluent outlet conduit 23 the inert gaseous material iswithdrawn either through conduit 23 or through conduit 53. The cooledpebbles from chamber 22 are elevated by elevator 21 in the same manneras described in the discussion of the device of Figure 1 of the drawingsand the pebbles are supplied through conduit 34 and through conduit ISin the same manner as described in connection with the device set forthas Figure 1 of the drawings. Heavy petroleum oil which is not retainedon the surface of pebbles within contact chamber 58 is separated fromthose pebbles and is allowed to pass into an excess oil separation'meanswhich comprises perforate pebble support member BI and collector chamber59. The oil is passed therefrom through conduit 39 into storage chamber42.

Referring particularly to the device set forth in Figure 5 of thedrawings, parts which are the same as those described in connection withFigures 1 and 4 of the drawings are indicated by like numerals. Thisdevice differs from those described above in that a perforate member 63is provided in a section of pebble outlet conduit 26, preferablydownstream of pebble flow controller 28. The perforations in thatconduit section are of such size as to allow pebbles of a particularsize to fall therethrough. It is preferred that pebbles having diametersin the range between A inch and A; inch be allowed to fall therethrough,while pebbles having diameters of inch and larger will be retainedwithin conduit 26 by perforate conduit member 63. Perforations inconduit member 63 generally range between inch and inch. Pebblecollector chamber 64 is provided around the perforate conduit member 63so as to collect the smaller diameter pebbles which pass through theperforate conduit member, and pebble conduit 65 extends between pebblecollector chamber 64 and the lower end portion of elevator 66 which issimilar to elevator 21. Elevator 66 is attached at its upper end portionto pebble conduit El which is in turn connected at its lower end portionto regeneration chamber 68. Gaseous efiluent conduit 69 is provided atthe upper end portion of chamber 68 and air inlet conduit H is providedin the lower end portion of that chamber. Gas heating chamber 12 isprovided below chamber 68 and is connected thereto by pebble conduit 73.Pebble outlet conduit 14 extends from the lower end portion of gasheating chamber 12 to the upper end portion of contact chamber 58. Airinlet conduit 15 is connected to the lower end portion of gas heatingchamber 12; Air outlet conduit 16 extends from the upper end portion ofchamber '52 to heating material inlet conduit 18 at the lower endportion of pebble heater chamber ll. Reactant material inlet conduit 47is connected at its outlet end to the lower end portion of pebble outletconduit 14 at a point adjacent its inlet to contact chamber 58.

In the operation of the device set forth as Figure 5 of the drawings,pebbles having a diameter of between inch and 1 inch are introduced intothe upper portion of chamber H and are heated in that chamber asdescribed above. Pebbles having a diameter of between A; inch and inchare introduced into the upper portion of contact chamber 58 and arecoated with the heavy petroleum charge stock as described above. Excessoil is separated from the oil coated pebbles in chamber 58 as describedin connection with the device of Figure 4 of the drawings, and the oilcoated pebbles are introduced into chamber 22, together with the highlyheated pebbles from chamber II and are admixed therein for reactionpurposes as heretofore described. Resulting reaction materials may bewithdrawn through elliuent outlet conduit 23 or effluent outlet conduit53.

No heat control gas is introduced into chamber 22 for the purpose oflowering and maintaining the temperature of pebbles therein. The pebblesare withdrawn from the lower end portion of chamber 22 through conduit26 and the flow thereof is controlled by pebble flow controller 28. Thepebbles of smaller diameter are separated from pebbles of a largerdiameter as they flow over the perforate conduit section 63, the smallerpebbles being gravitated therethrough into pebble collector chamber 64.The larger pebbles are elevated by means of elevator 21 and areintroduced into the upper portion of chamber H. The smaller pebbles aresupplied by conduit 65 to the lower portion of elevator 66 by which theyare elevated to the upper end portion of conduit 61 through which theyare gravitated into the upper portion of regeneration chamber 68. Air isintroduced into the lower portion of regeneration chamber 58 throughconduit H and any carbonaceous or tarry material is oxidized from thesurface of the pebbles and gaseous efliuent material is removed fromregeneration chamber 68 through efiluent conduit 69.

The pebbles from which the carbonaceous or tarry material has beenremoved are gravitated through conduit l3 into chamber 12. Air isintroduced into the lower portion of chamber 12 through inlet conduit 15and flows upwardly therethrough countercurrent the flow of pebblestherein. The pebbles are cooled in a direct heat exchange with the airin chamber 12 and are supplied in that cooled condition to the upperportion of chamber 58 through conduit 14. The air which is heated in thedirect heat exchange in chamber 12 is supplied by conduit 16 to heatingmaterial inlet conduit l8 wherein it is admixed with a combustible fuelmaterial.

It is obvious that the air and fuel could be supplied to a combustionzone external of pebble heater chamber H, but for the purpose ofsimplicity Figure diagrammatically shows a common conduit for fuel andair into the lower portion of chamber ll. Reactant material isintroduced onto the surface of the cooled pebbles at the lower endportion of conduit 14. A heating means, either externally or internallypositioned may be provided in heat exchange relation with the lowerportion of charge stock storage chamber 42. In most situations, thatwill not be necessary, however, for the oil separated from pebbleswithin chambers 29 and 58 will ordinarily carry suflicient heat tomaintain the temperature of the oil in chamber 42 in a flowable state.

Specific example A heavy residual oil having an API gravity of 17.9 issprayed into the upper portion of a contact chamber and onto the surfaceof pebbles which are at a temperature of about 700 F. The oil isintroduced into the contact chamber at a rate of about 50 pounds perhour. The oil coated pebbles are gravitated through the contact chamberand into the upper portion of a reaction chamber at a rate of about 600pounds per hour, carrying about 42.5 pounds of oil per hour. Steam isintroduced into the lower portion of the reaction chamber at a rate ofabout 43 pounds per hour and pebbles which are at a temperature of about2500 F. are gravitated into the upper portion of the reaction chamber inadmixture with the oil coated pebbles at a rate of about 1400 pounds perhour. Heat from the hotter pebbles raises the oil within the reactionchamber to a reaction temperature such that vaporous and gaseousproducts, amounting to about 93.4 weight per cent of the feed, areobtained by withdrawing them together with the steam from the upperportion of the reaction chamber. The type of products produced and theirrelative amounts are set forth as follows (weight per cent based on thefeed):

Percent Gases (C4 and lighter hydrocarbons, and

H2) 22.4 Gasoline (400 F. end point) 18.5 Light gas oil (400 F.-750 F.)10.7 Heavy gas oil (750 F.-900 F.) 10.9 Higher boiling materials (900F.+) 30.9

The composition of the gaseous products (C4 and lighter) is shown in thefollowing tabulation:

Mol percent A portion of the feed material is converted to coke (about6.6 weight per cent of the feed under these conditions) and is depositedon the surface of the pebbles. A portion of the coke bearing pebbleswhich have been reduced to a temperature of about 700 F. within thereaction chamber are returned to the contact chamber in which they areonce again coated with heavy oil. The

remaining portion of coke bearing pebbles are passed to a pebble heatingchamber in which the coke is burned from the surface thereof, the cokesupplying a portion of the fuel required of the process. In this manner,an excessive accumulation of coke on the pebbles is prevented. Thepresence of coke on some of the pebbles passing through the reactionchamber does not interfere with the formation of the oil coating on suchpebbles and random distribution of the coked pebbles between the contactand heating chambers of the system insures adequate coke removal fromthe system.

Various modifications of this invention will be apparent to thoseskilled in the art upon study of the above disclosure and the drawingsSuch modifications will be apparent to those skilled in the art and arebelieved to fall within the spirit and scope of this disclosure. 7

I claim:

1. A method for converting a heavy petroleum fraction to lighterhydrocarbon materials which comprises in combination the steps ofpassing a first portion of pebbles into the upper portion of a pebbleheating zone; passing a hot fiuid heating material through said heatingzone so as to raise said first pebbles to a temperature within the rangeof from 2000 F. to 3200 F. removing gaseous effluent materials from saidpebble heating zone; passing said heated first pebbles into a reactionzone; by-passing said heating zone with a second portion of pebbles andintroducing said second portion of pebbles into a contact zone;introducing said heavy petroleum into said contact zone and coating saidsecond pebbles with only said heavy petroleum; passing said petroleumcoated second pebbles from said contact zone into said reaction zone ata temperature within the range of from 300 F. to 800 F.; admixing saidheated first pebbles and said petroleum coated second pebbles in saidreaction zone and raisingsaid heavy petroleum to reaction temperaturethereby; removing gaseous reaction products from said reaction zone;removing said pebbles from said reaction zone; returning a first portionof said pebbles to said pebble heating zone; and returning the balanceof said pebbles to said contact zone.

2. A method for converting a heavy petroleum fraction to lighterhydrocarbon materials which comprises in combination the steps ofpassing a first portion of pebbles into the upper portion of a pebbleheating zone; passing a hot gaseous heating material through saidheating zone so as to raise said first pebbles to a temperature withinthe range of from 2500 F. to 3000 F.; removing gaseous effluent materialfrom said pebble heating zone; passing said heated first pebbles intothe upper portion of a reaction zone and downwardly therethrough;by-passing' said heating zone with a second portion of pebbles andintroducing said second portion of pebbles into a contact zone;introducing said heavy petroleum into said contact zone and coating saidsecond pebbles with only said heavy petroleum; passing said petroleumcoated second pebbles from said contact zone into said reaction zone ata temperature within the rangeof from 350 F. to 700 F.; admixing saidheated first pebbles and said petroleum coated second pebbles in saidreaction zone and thereby raising said heavy petroleum to reactiontemperature within the range of from 1250 F. to 1600 F. removing gaseousreaction products from said reaction zone; removing said pebbles fromthe lower por- 11 tion of said reaction zone; returning a first portionof said pebbles to the upper portion of said pebble heating zone; andreturning the balance of said pebbles to said contact zone.

3. The method of claim 2, wherein the ratio of said petroleum coatedsecond pebbles to said heated first pebbles is within the range of from1:1 to 1:3.

4. The method of claim 2, wherein the temperature of said secondpetroleum coated pebbles and said heated first pebbles at the point ofintroduction into said reaction zone and the ratio between said secondand first pebbles is such that said heavy petroleum is raised to areaction temperature within the range of 1400 F. to 1600 F.

5. The method of claim 2, wherein heavy petroleum in addition to thatcoating said second pebbles is introduced into the upper portion of saidreaction zone; and the temperature of said second petroleum coatedpebbles and said heated first pebbles at the point of introduction intosaid reaction zone, the ratio between said second and first pebbles, andthe quantity of said additional heavy petroleum is such that said heavypetroleum is raised to a reaction temperature within the range of 1400F. to 1600" F.

6. A method for converting a heavy petroleum fraction, having an APIgravity within the range of to 25, to lighter hydrocarbon materialswhich comprises in combination the steps of passing a first portion ofpebbles into the upper portion of a pebble heating zone; passing a hotgaseous heating material through said heating zone so as to raise saidfirst pebbles to a temperature within the range of from 2500 F. to 3000F.; removing gaseous efiiuent material from said pebble heating zone;passing said heated first pebbles into the upper portion of a reactionzone and downwardly therethrough; by-passing said heating zone with asecond portion of pebbles and introducing said second portion of pebblesinto the upper portion of a contact zone and downwardly therethrough;introducing said heavy petroleum into the upper portion of said contactzone; passing said heavy petroleum downwardly through said contact zonein direct contact with said second pebbles, thereby coating said secondpebbles with only said heavy petroleum; separating said petroleum coatedsecond pebbles and excess petroleum; returning said excess petroleum tothe upper portion of said contact zone; passing said petroleum coatedsecond pebbles from said contact zone into said reaction zone at atemperature within the range of from 350 F. to 700 F.; admixing saidheated first pebbles and said petroleum coated second pebbles in saidreaction zone; removing said pebbles from the lower portion of saidreaction zone; and returning a first portion of said pebbles to theupper portion of said pebble heating zone 7. A heavy oil cracking systemcomprising ir combination a first closed pebble chamber; first pebbleinlet means in the upper portion of said first chamber; gaseous efiluentoutlet means in the upper portion of said first chamber; heatingmaterial inlet means in the lower portion of said first chamber; asecond closed pebble chamber chamber; second pebble inlet means in theupper end portion of said third chamber; first oil inlet means in theupper end portion of said third chamber; second pebble outlet meansintermediate the ends of said third chamber; second pebble conduit meansextending between said pebble outlet means in said third chamber and thetop portion of said second chamber; excess oil separation meansconnected to and sloping in a direction common with said second pebbleconduit means; an oil supply system connected to said oil inlet means insaid third chamber; first oil conduit means extending between said oilseparation means and said oil supply system; a plurality of perforationsin the lower portion of a laterally extending section of said firstpebble outlet means, said perforations having a lateral dimension in therange of from inch to inch; a pebble collector chamber enclosing thelower side of said perforate section of said second pebble outlet means;third pebble outlet means in the lower portion of said pebble collectorchamber; and elevator extending between said first pebble outlet meansand said first pebble inlet means; a fourth closed pebble chamber abovesaid third chamber; third pebble inlet means in the upper portion ofsaid fourth chamber; an elevator extending between said third pebbleoutlet means and said third pebble inlet means; a gaseous eiiluentoutlet in the upper portion of said fourth chamber; a gaseous materialinlet conduit in the lower portion of said fourth chamber; a fifthclosed pebble chamber below said fourth chamber; a pebble conduitextending between the lower portion of said fourth chamber and the upperportion of said fifth chamber; third pebble conduit means extendingbetween the lower portion of said fifth chamber and said second pebbleinlet means; a gaseous material inlet in the lower portion of said fifthchamber; and a gaseous material conduit extending between the upperportion of said fifth chamber and said heating material inlet means insaid first chamber.

8. The heavy oil cracking system of claim '7, wherein said first pebbleconduit means and said second pebble conduit means form a common pebbleinlet to said second chamber.

9. The heavy oil cracking system of claim 8, wherein an auxiliary oilinlet is provided in the upper portion of said second chamber andadjacent the outlet of said first pebble conduit means; and second oilconduit means extending between said oil supply system and said secondoil outlet means.

10. The heavy oil cracking system of claim 7, wherein a bafiie member,smaller in diameter than the inner diameter of said first pebble conduitmeans, is positioned in that conduit means; and, said second pebble.conduit means extends from the pebble outlet. means in said thirdchamber to a place in said first conduit means directly over saidbaffle.

11. The heavy oil cracking system of claim 7, wherein said excess oilseparation means comprises. a perforate pebble support member formingthe bottom closure of said third chamber, and a collector chamberenclosing the lower portion of said perforate pebble support member; andsaid second pebble conduit means extending from said third chamber at apoint adjacent the top surface of said perforate pebble support member.

12. A method for converting a heavy petroleum fraction having an APIgravity within the range 13 of 15 to 20, to lighter hydrocarbonmaterials which comprises in combination the steps of passing a firstportion of pebbles into the upper portion of a pebble heatin zone;passing a hot gaseous heating material through said heating zone so asto raise said first pebbles to a temperature within the range of from2509" F. to 3000 F. removing gaseous effluent material from said pebbleheating zone; passing said first pebbles into the upper portion of areaction zone and downwardly therethrough; passing a second portion ofpebbles into the upper portion of a contact zone and downwardlytherethrough; introducing said heavy petroleum into the upper portion ofsaid contact zone; passing said heavy petroleum downwardly through saidcontact zone in direct contact with said second pebbles, thereby coatingsaid second pebbles with said petroleum; separating saidpetroleum-coated second pebbles and excess petroleum; returning saidexcess petroleum to the upper portion of said contact zone; passing saidpetroleum-coated second pebbles from said contact zone into saidreaction zone at a temperature within the range of from 359 F. to 700EH; admixing said heated first pebbles and said petroleum-coated secondpebbles in said reaction zone; removing said pebbles from the lowerportion of said reaction zone; returning a first portion of said pebblesto the upper portion of said pebble heating zone; passing the balance ofsaid pebbles into the upper portion of a regeneration zone anddownwardly therethrough; passing air into the lower portion of saidregeneration zone and upwardly therethrough countercurrent to the flowof pebbles therethrough; oxidizing any carbonaceous deposits on saidpebbles in said regeneration zone; removing gaseous efiiuent from saidregeneration zone; passing said pebbles from the lower portion of saidregeneration zone into the upper portion of a gas heating zone anddownwardly therethrough; passing air through said gas heating zone indirect heat exchange with said pebbles therein, whereby said air isheated and said pebbles are cooled; passing said cooled pebbles into theupper portion of said contact zone; removing said heated air from saidgas heating zone; passing said heated air and a combustible fuel to acombustion zone; burning said fuel in said combustion zone; andintroducing resulting hot combustion gases into the lower portion ofsaid pebbles heating zone as said hot gaseous heating material.

13. A heavy oil cracking system comprising in combination a first closedpebble chamber; first pebble inlet means in the upper portion of saidchamber; gaseous efiluent outlet means in the upper portion of saidfirst chamber; heating material inlet means in the lower portion of saidfirst chamber; a second closed pebble chamber below said first chamber;first pebble conduit means extending between the lower portion of saidfirst chamber and the top portion of said second chamber; gaseous emuentoutlet means in the upper portion of said second chamber; pebble outletmeans in the lower portion of said second chamber; a third closed pebblechamber above said second chamber; pebble inlet means in the upper endportion of said third chamber; first oil inlet means in the upper endportion of said third chamber; pebble outlet means in the lower portionof said third chamber; second pebble conduit means extending downwardlybetween said pebble outlet means in said third chamber and the topportion of said second chamber; excess oil separation means comprising aperforate pebble support member forming the bottom closure of said thirdchamber, and a collector chamber enclosing the lower portion of saidperforate pebble support member, connected to and sloping in a directioncommon with said second pebble conduit means, said second pebble conduitmeans extending from said third chamher at a point adjacent to the topsurface of said perforate support member; an oil supply system connectedto said oil inlet means in said third chamber; first oil conduit meansextending between said oil separation means and said oil supply system;and a pebble transfer means extending between said pebble outlet meansin said second chamber and said pebble inlet means in said first andthird chambers.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,405,395 Bahlke et al Aug. 6, 1946 2,441,170 Rose et a1. May11, 1948 2,448,922 Simpson et al. Sept. '7, 1948 2,486,627 Arnold Nov.1, 1949 2,490,336 Croeley, Jr. Dec. 6, 1949 2,492,999 Lassiat Jan, 3,1950 2,513,294 Eastwood et a1. July 4, 1950 2,531,356 Evans Nov. 21,1950

1. A METHOD FOR CONVERTING A HEAVY PETROLEUM FRACTION TO LIGHTERHYDROCARBON MATERIALS WHICH COMPRISES IN COMBINATION THE STEPS OFPASSING A FIRST PORTION OF PEBBLES INTO THE UPPER PORTION OF A PEBBLEHEATING ZONE; PASSING A HOT FLUID HEATING MATERIAL THROUGH SAID HEATINGZONE SO AS TO RAISE SAID FIRST PEBBLES TO A TEMPERATURE WITHIN THE RANGEOF FROM 2000* F. TO 3200* F.; REMOVING GASEOUS EFFLUENT MATERIALS FROMSAID PEBBLE HEATING ZONE; PASSING SAID HEATED FIRST PEBBLES INTO AREACTION ZONE; BY-PASSING SAID HEATING ZONE WITH A SECOND PORTION OFPEBBLES AND INTRODUCING SAID SECOND PORTION OF PEBBLES INTO A CONTACTZONE; INTRODUCING SAID HEAVY PETROLEUM INTO SAID CONTACT ZONE ANDCOATING SAID SECOND PEBBLES WITH ONLY SAID HEAVY PETROLEUM; PASSING SAIDPETROLEUM COATED SECOND PEBBLES FROM SAID CONTACT ZONE INTO SAIDREACTION ZONE AT A TEMPERATURE WITHIN THE RANGE OF FROM 300* F. TO 800*F.; ADMIXING SAID HEATED FIRST PEBBLES AND SAID PETROLEUM COATED SECONDPEBBLES IN SAID REACTION ZONE AND RAISING SAID HEAVY PETROLEUM TOREACTION TEMPERATURE THEREBY; REMOVING GASEOUS REACTION PRODUCTS FROMSAID REACTION ZONE; REMOVING SAID PEBBLES FROM SAID REACTION ZONE;RETURNING A FIRST PORTION OF SAID PEBBLES TO SAID PEBBLE HEATING ZONE;AND RETURNING THE BALANCE OF SAID PEBBLES TO SAID CONTACT ZONE.
 13. AHEAVY OIL CRACKING SYSTEM COMPRISING IN COMBINATION A FIRST CLOSEDPEBBLE CHAMBER; FIRST PEBBLE INLET MEANS IN THE UPPER PORTION OF SAIDCHAMBER; GASEOUS EFRFLUENT OUTLET MEANS IN THE UPPER PORTION OF SAIDFIRST CHAMBER; HEATING MATERIAL INLET MEANS IN THE LOWER PORTION OF SAIDFIRST CHAMBER; A SECOND CLOSED PEBBLE CHAMBER BELOW SAID FIRST CHAMBER;FIRST PEBBLE CONDUIT MEANS EXTENDING BETWEEN THE LOWER PORTION OF SAIDFIRST CHAMBER AND THE TOP PORTION OF SAID SECOND CHAMBER; GASEOUSEFFLUENT OUTLET MEANS IN THE UPPER PORTION OF SAID SECOND CHAMBER PEBBLEOUTLET MEANS IN THE LOWER PORTION OF SAID SECOND CHAMBER; A THIRD CLOSEDPEBBLE CHAMBER ABOVE SAID SECOND CHAMBER; PEBBLE INLET MEANS IN THEUPPER END PORTION OF SAID THIRD CHAMBER; FIRST OIL INLET MEANS IN THEUPPER END PORTION OF SAID THIRD CHAMBER; PEBBLE OUTLET MEANS IN THELOWER PORTION OF SAID THIRD CHAMBER; SECOND PEBBLE CONDUIT MEANSEXTENDING DOWNWARDLY BETWEEN SAID PEBBLE OUTLET MEANS IN SAID THIRDCHAMBER AND THE TOP PORTION OF SAID SECOND CHAMBER; EXCESS OILSEPARATION MEANS COMPRISING A PERFORATE PEBBLE SUPPORT MEMBER FORMINGTHE BOTTOM CLOSURE OF SAID THIRD CHAMBER, AND A COLLECTOR CHAMBERENCLOSING THE LOWER PORTION OF SAID PERFORATE PEBBLE SUPORT MEMBER,CONNECTED TO AND SLOPING IN A DIRECTION COMMON WITH SAID SECOND PEBBLECONDUIT MEANS, SAID SECOND PEBBLE CONDUIT MEANS EXTENDING FROM SAIDTHIRD CHAMBER AT A POINT ADJACENT TO THE TOP SURFACE OF SAID PERFORATESUPPORT MEMBER; AN OIL SUPPLY SYSTEM CONNECTED TO SAID OIL INLET MEANSIN SAID THIRD CHAMBER; FIRST OIL CONDUIT MEANS EXTENDING BETWEEN SAIDOIL SEPARATION MEANS AND SAID OIL SUPPLY SYSTEM; AND A PEBBLE TRANSFERMEANS EXTENDING BETWEEN SAID PEBBLE OUTLET MEANS IN SAID SECOND CHAMBERAND SAID PEBBLE INLET MEANS IN SAID FIRST AND THIRD CHAMBERS.